Laptop power emergency

September 4, 2008 11:29 AM

Laptop power question.

I am away from home and need to power my Lenovo T61 (Nvida graphics card) laptop. I went to radio shack where they sold me an iGo "everywhere 85" adapter. It says it is compatible with the T60, but does not mention the T61. It has a "tip" that is the right size, and when I plug it in, it seems to charge just fine. The iGo website seems to think I need an "everywhere 130" adapter. I can't tell, or don't understand, what the difference is. Am i going to fry my laptop with the everywhere 85?

posted by dpx.mfx to computers & internet (7 comments total)

The difference is the power (in Kilowatts). You're providing ~85W with your adapter, whereas the suggested 130 would provide 130W. Basically, it'll take a little longer to charge, you might be slightly reducing the life of the battery, and if you're burning DVDs while playing some 3D-intense game, it might start losing power even though it's plugged in. But other than that, it's fine.
posted by one_bean at 11:46 AM on September 4, 2008

thanks one_bean. I had no idea that the number was kws. That makes sense. Since I'm underpowering it instead of overpowering it, I assume I won't fry anything. Whew. (Also good because the local radio shack -- the only option for any power device out here -- doesn't have the 130, so I'd sort of be SOL.)
posted by dpx.mfx at 11:49 AM on September 4, 2008

The official Lenovo adapter for the T60 and T61 is 90W. The 85W iGo adapter is close enough to be fine.
posted by zsazsa at 12:07 PM on September 4, 2008

Oh. Hm. The iGo website says the Everywhere 85 supplies 70W continuous power, and the Everywhere 130 supplies 90W. Talk about bad model numbering. That said... you're probably still fine.
posted by zsazsa at 12:12 PM on September 4, 2008

The watts is the voltage times the amps. So if you look at the label on the adapter that came with your laptop, it might say something like 110-240V AC 50-60Hz, output 20V DC 4.2A

The V DC number is Volts (Direct Current).
The A number is Amperes.

Multiply these and you find out how many watts the adapter can provide. (In the example above, 20V x 4.2A = 84 W, so the iGo 85, at 85W output would be a good fit - it equals or exceeds the hypothetical adapter we're trying to replace.

The adapter is designed to be able to provide more power than the laptop normally uses - if you're charging a completely flat battery AND playing a graphics intensive game AND it is CPU intensive AND you're running the DVD, AND the screen is on full brightness, etc, then you are drawing a lot of power.
But normally you don't do all these things, so even an adapter that only provides 70% of the power that the proper adapter provides, will still work under a lot of situations, and even when it doesn't, it may result in the laptop being powered but unable to charge the battery.

If you notice things like the screen brightness flickering in time with the charge light going on and off, you're exceeding the power the iGo can provide, so keep an eye on things, or reduce your CPU activity and turn down the screen brightness, etc.
posted by -harlequin- at 12:12 PM on September 4, 2008

Note also that you want the voltage an adaptor provides to be within a few volts of that of the original adaptor. If an adaptor is 40V 2.1A, it's still an 84W adapter, but it would fry the computer. Laptops are generally 15-21V, so I'm guessing the iGO either has some voltage settings, or sits at about 18V.

The Amperes can be as high as you like - amperes are how much the adaptor can provide if the laptop requests it, whereas voltage is forced on the laptop by the adaptor.
posted by -harlequin- at 12:21 PM on September 4, 2008

FWIW, the adapter, which is insanely hot at the moment and makes a noise like power lines, says:

input: 100-240 V ~ 2A 50-60 Hz
output: 15-24V ~~ 65W Max

oddly (or maybe not?) it has different numbers for when use on planes and in cars. There it says:

DC Adapter:
Input: 11.5-16V ~8A
output: 15-24V ~~ 70W Max
posted by dpx.mfx at 12:40 PM on September 4, 2008